Ester-functional monomers and polymers prepared from same

ABSTRACT

An unsaturated ester monomer having the structure: ##STR1## wherein R 1  is hydrogen or methyl; R 2 , R 3  and R 4  are each independently lower alkyl of 1 to about 4 carbons; and Z is nothing or is a divalent radical having 1 to about 20 carbons.

This is a divisional of application Ser. No. 08/176,609, filed on Jan.03, 1994, (now U.S. Pat. No. 5,349,080).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention involves novel polymerizable monomers having pendentester groups and polymers prepared from those monomers. The monomershave the structure: ##STR2## wherein R¹ is hydrogen or methyl; R² R³ andR⁴ are each independently lower alkyl of 1 to about 4 carbons; and Z isnothing or is a divalent alkyl radical having 1 to about 20 carbonatoms. Preferred divalent alkyl radicals are methylene chains --(--CH₂--)_(n) -- wherein n is 1 to 20.

This invention also relates to polymers obtained by polymerizing, underfree radical addition polymerization conditions, (i) the unsaturatedester monomer of this invention; and (ii) optionally, at least one otherunsaturated monomer copolymerizable with the unsaturated ester monomer.The monomers are also useful as reactive diluents and as precursors foracid and/or anhydride-functional monomers.

2. Description of the Prior Art

Unsaturated, polymerizable esters, such as butyl acrylate, methylmethacrylate, methyl crotonate, or ethyl tiglate and polymers orcopolymers incorporating these materials are known in the art. By theselection of one or more of these esters, the characteristics of apolymer may be tailored to provide a desired glass transitiontemperature, hardness, flexibility or other desired property. The priorart has not, however, taught polymers obtained by the polymerization ofthe novel styrene-based ester monomers of this invention.

BRIEF SUMMARY OF THE INVENTION

This invention involves polymerizable unsaturated monomers havingpendent ester functionality, and to polymers derived by polymerizing theester monomer through its unsaturation either as a homopolymer or,preferably, in combination with one or more additional copolymerizablemonomers. The esters of this invention can be utilized to alter theglass transition temperature, solubility, hardness, flexibility,crystalinity or other physical or performance property of a copolymer byincorporating these novel monomers into the polymer backbone by freeradical polymerization. Furthermore, since the unsaturated esters ofthis invention are styrene based materials, their reactivity ratios withother polymerizable monomers such as styrene and (meth)acrylate monomersunder free radical polymerization conditions will be different than thereactivity ratios of the common prior art (meth)acrylate esters withthose same copolymerizable monomers. Therefore, the monomers of thisinvention can provide a way to incorporate ester side chains whilealtering the arrangement of other monomers along the polymeric backbonecompared to the use of the common prior art unsaturated esters.Additionally, since the ester groups of the monomer can be, if desired,fully or partially hydrolyzed, either before or after polymerization toproduce acid-functional monomers and/or polymers, these ester monomersof this invention have special utility when utilized as precursors forthose acid-functional materials.

Accordingly, one object of this invention is to provide novel styrenebased ester monomers. Another object is to provide polymers andcopolymers incorporating the ester monomers. Another object is toprovide new unsaturated esters which are readily hydrolyzable to acidfunctionality. These and other objects of the invention will becomeapparent from the following discussions.

DETAILED DESCRIPTION OF THIS INVENTION

The unsaturated styrene based ester monomers of this invention can beconveniently prepared by the reaction of the anion of atrialkyl-1,1,2-ethanetricarboxylate (such astriethyl-1,1,2-ethanetricarboxylate), with a vinyl benzene alkyl halide(such as vinyl benzyl chloride).

The vinyl benzene alkyl halide has the general structure: ##STR3##wherein R¹ and Z are as defined above and X is a halogen atom. The vinylbenzene alkyl halides of various lengths of Z can be readily prepared bya variety of methods known in the art. For example, Grignard reactionsynthesis of the vinyl benzene alkyl halides are representatively setforth in M. L. Hallensleben, Angew. Makronol. Chem., 31 147 (1973), andMontheard et al. J. Polym. Sci. Part A., Polym. Chem., 27 (8), 2539(1989). For cost and availability of starting materials, it isespecially preferred that Z be nothing or be lower alkyl of 1 to about 4carbons. Vinyl benzyl chloride, where Z is nothing, R¹ is hydrogen and Xis chlorine, is especially preferred.

The trialkyl-1,1,2-ethanetricarboxylate has the general structure:##STR4## wherein R², R³ and R⁴ are lower alkyl of 1 to about 4 carbons.Due to cost and reactivity, triethyl-1,1,2-ethanetricarboxylate isespecially preferred.

The reaction to produce the preferred ester-functional monomer isrepresentatively shown below wherein thetrialkyl-1,1,2-ethanetricarboxylate istriethyl-1,1,2-ethanetricarboxylate and the vinyl benzene alkyl halideis vinyl benzyl chloride: ##STR5##

The preparation of the anion of the trialkyl-1,1,2-ethanetricarboxylateis conveniently accomplished by mixing ethanolic sodium ethoxide withthe tricarboxylate and refluxing the solution for five to ten minutes.Typically the sodium ethoxide will be present at a level to provideabout 0.8 to about 1.1 moles of sodium ethoxide for each mole oftricarboxylate. The anion of the tricarboxylate can then be reacted withthe vinyl benzene alkyl halide by mixing the two materials in anapproximately 1 to 1 mole ratio and by maintaining the reaction atreflux, in the presence of small amounts (e.g. 500 ppm of the totalreaction mixture) of polymerization inhibitors, for 1 to about 3 hoursto prepare the vinyl benzene alkyl-1,2-ethane tricarboxylate.

In one use of the monomer of the invention, the vinyl benzenealkyl-1,1,2-ethane tricarboxylate could be hydrolyzed to produce thecorresponding tricarboxylic acid by reaction with base, such as sodiumhydroxide or potassium hydroxide, followed by acidification.Alternatively, the hydrolysis can be accomplished by direct reaction ofthe tricarboxylate with aqueous acid such as aqueous hydrochloric acid.Base hydrolysis is generally preferred and can be readily conducted byadmixing an aqueous and/or ethanolic solution of sodium hydroxide orpotassium hydroxide and maintaining the reaction mixture at reflux untilthe reaction is complete (typically 3 to 5 hours). The salt product canbe collected by filtration and the tricarboxylic acid is then generatedby acidifying an aqueous solution of the salt to a pH less than about 3,typically by using dilute acid such as aqueous hydrochloric acid.

The polymerization of the novel monomers of this invention either aloneor with other unsaturated copolymerizable monomers, such as acrylic ormethacrylic monomers or styrene, proceeds at excellent yield and canproduce polymers having excellent performance characteristics.

The polymers which incorporate the monomers of this invention couldconveniently be prepared by polymerizing the styrene based estermonomer, and, normally, at least one other copolymerizable monomer underfree radical addition polymerization conditions. Typically, thepolymerization would be conducted in an inert solvent and in thepresence of an initiator, such as a peroxide or azo compound, attemperatures ranging from 35° C. to about 200° C., and especially 75°C., to about 150° C. Representative initiators include di-t-butylperoxide, cumene hydroperoxide, and azobis(isobutyronitrile).

The mixture of monomers used to prepare the polymers would typicallycomprise from 1 to about 100, and especially 5 to about 85 percent byweight of the styrene based ester monomer. The remainder of the mixtureof monomers would be comprised of at least one other unsaturated monomercopolymerizable with the styrene based ester monomer. If it is desiredto generate a reactive polymer, suitable unsaturated monomers containingpotentially reactive sites such as hydroxy, epoxy, acid or amine groupscan be incorporated into the polymer along with the styrene basedesters. Typically, the styrene based ester monomers would becopolymerized with one or more monomers having ethylenic unsaturationsuch as:

(i) acrylic, methacrylic, crotonic, tiglic, or other unsaturated acidsor derivatives thereof, such as: acrylic acid, methacrylic acid, methylacrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butylacrylate, isobutyl acrylate, ethylhexyl acrylate, amyl acrylate, 3,5,5-trimethylhexyl acrylate, methyl methacrylate, ethyl methacrylate,propyl methacrylate, dimethylaminoethyl methacrylate, isobornylmethacrylate, ethyl tiglate, methyl crotonate, ethyl crotonate,2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropylacrylate, 4-hydroxybutyl methacrylate, 2-hydroxypropyl methacrylate,3-hydroxybutyl acrylate, 4-hydroxypentyl acrylate, 2-hydroxyethylethacrylate, 3-hydroxybutyl methacrylate, 2-hydroxyethyl chloroacrylate,diethylene glycol methacrylate, glycidyl acrylate, glycidylmethacrylate, tetra ethylene glycol acrylate, etc.;

(ii) vinyl compounds such as vinyl acetate, vinyl propionate, vinylbutyrate, vinyl isobutyrate, vinyl benzoate, vinyl m-chlorobenzoate,vinyl p-methoxybenzoate, vinyl α-chloroacetate, vinyl toluene, vinylchloride, paravinyl benzyl alcohol, etc.;

(iii) styrene-based materials such as styrene, α-methyl styrene, α-ethylstyrene, α-bromo styrene, 2,6- dichlorostyrene, etc.;

(iv) allyl compounds such as allyl chloride, allyl acetate, allylbenzoate, allyl methacrylate, etc.;

(v) other copolymerizable unsaturated monomers such as ethylene,acrylonitrile, methacrylonitrile, dimethyl maleate, isopropenyl acetate,isopropenyl isobutyrate, acrylamide, methacrylamide, and dienes such as1,3-butadiene, etc.

The free radical addition polymers of this invention could typically beused as lacquers or as reactive polymers and would have application inadhesives, coatings, inks, plastics, chemical additives and fibers.Where the polymers are required to be of the reactive crosslinking type,suitable functional monomers which can be used include acrylic ormethacrylic acid, hydroxy ethyl acrylate, 2-hydroxy propyl methacrylate,glycidyl acrylate, tertiary-butyl amino ethyl methacrylate, etc. Thepolymer may, in such a case, be used in combination with a crosslinkingagent which would be reactive with the functional groups of the polymer.Typical crosslinking agents would include polyisocyanates, polyepoxidesor nitrogen resins such as the condensates of an aldehyde such asformaldehyde with a nitrogenous compound such as urea, melamine orbenzoguanamine or a lower alkyl ether of such a condensate.

The following examples have been selected to illustrate specificembodiments and practices of advantage to a more complete understandingof the invention. Unless otherwise stated, "parts" means parts-by-weightand "percent" is percent-by-weight. The starting raw materials utilizedin these examples are commercially available. The vinyl benzyl chlorideis a 70/30 meta/para isomer commercially available from Dow ChemicalCompany. The sodium metal, diethyl malonate, ethyl chloroacetate, aceticanhydride, butylated hydroxy toluene, and, unless otherwise indicated,the triethyl-1,1,2-ethanetricarboxylate, were obtained from AldrichChemical Company. The absolute ethanol was obtained from USI-QuantumChemical Company.

EXAMPLE A Triethyl-1,1,2,-ethane tricarboxylate

A solution of sodium ethoxide in ethanol was prepared by slowly adding559.4 g sodium metal into 7890 g of absolute ethanol. Next, 3891.9 g ofdiethyl malonate was added to the ethanol solution over 45 minutes at aninitial temperature of 25° C. The mixture was homogenized by heating at50° C. for 40 minutes. Next, 3000 g ethyl chloroacetate was slowly addedover approximately 90 minutes, while the reaction mixture was maintainedat 40°-50° C. with occasional warming. The mixture was then heated atreflux for 2 hours, then cooled to room temperature.

The mixture was worked-up by stripping off approximately two-thirds ofthe ethanol (˜750-800 ml). The residue was then washed with water andextracted with toluene. The toluene solution was dried over magnesiumsulfate, followed by removal of the toluene to give a dark red residue.The product residue was distilled under reduced pressure to give 3252 g(approximately 54.3% yield) of triethyl-1,1,2-ethane tricarboxylate in˜97% purity.

EXAMPLE B Triethyl 1-(3/4-vinyl benzyl)-1,1,2-ethane tricarboxylate

An ethanol solution of sodium ethoxide was prepared by adding 283 g ofsodium metal over 8 hours to 6404 g of ethanol (maximum temperature 60°C.). Triethyl-1,1,2-ethane tricarboxylate (Example A, 3156.9 g) was thenadded over 20 minutes to the ethanol solution (maximum temperature 30°C.). The mixture was then heated at reflux for 5-10 minutes, then cooledto 25° C. Next, 1816.3 g of vinyl benzyl chloride was added over 40minutes, while keeping the temperature under 35° C. A small amount ofbutylated hydroxy toluene inhibitor was added. The mixture was heated atreflux for 2 hours and 20 minutes and then allowed to cool to roomtemperature.

The reaction mixture was neutralized (pH˜7) with glacial acetic acid,and approximately two-thirds of the ethanol was stripped off underreduced pressure. Sodium chloride was filtered off. The unpurifiedstyryl methylene triester/ethanol solution (63.6% NVM in ethanol) wasthen utilized to produce the corresponding tricarboxylic acid as shownin Example E.

EXAMPLE C Triethyl 1-(3/4-vinyl benzyl)-1,2-ethane tricarboxylate

A sodium ethoxide/ethanol solution was prepared by slowly adding 16.02 gof sodium metal to 365 g of absolute ethanol with slow stirring. Themixture was then heated at reflux for 5-10 minutes.Triethyl-1,1,2-ethane tricarboxylate (180 g from Aldrich ChemicalCompany) was added over 20 minutes to the mixture at room temperature.The mixture was heated at reflux for 5-10 minutes, then cooled to 25° C.Next, 112.9 g of vinyl benzyl chloride was added over 20 minutes(maximum temperature of the reaction mixture was 45° C. ). A smallamount of butylated hydroxy toluene inhibitor was added. The mixture washeated to reflux for 2 hours, then cooled to room temperature.

The reaction mixture was neutralized (pH˜7) with glacial acetic acid.About two-thirds of the ethanol was stripped off under reduced pressure.Six hundred sixty-five milliliters of deionized water was added and theproduct was extracted with toluene. The combined toluene extracts weredried over sodium sulfate. Removing the volatiles with rotaryevaporation produced 255.2 g of triethyl-1-(3/4-vinylbenzyl)-1,1,2-ethane tricarboxylate as a yellow liquid in an isolatedyield of 96% of theory. NMR and infrared spectral data confirmed thestructure of the tricarboxylate product.

One potential utility for the styrene based ester monomers of thisinvention is their use as precursors for acid-functional monomers andpolymers. Acid-functional monomers and polymers are useful for theirreactivity with other groups such as hydroxyl or epoxy and also can beneutralized with a base such as ammonia to provide water dispersibility.Example D and E show the production of such acid-functional monomers.

EXAMPLE D 1-(3/4-Vinyl benzyl)-1,1,2-ethane tricarboxylic acid

An aqueous/ethanolic potassium hydroxide solution was prepared by slowlymixing 2805 ml of absolute ethanol and 147.5 ml of deionized water. Asmall amount of butylated hydroxy toluene inhibitor was added. Potassiumhydroxide (363 g) was added slowly keeping the temperature below reflux.The mixture was then cooled to 30° C. and 240 g, (approximately 0.662tool) of the crude product of the vinyl benzyl triester of Example C wasquickly added. The mixture rapidly turned cloudy and then becamehomogeneous upon heating to reflux. An additional small amount ofbutylated hydroxy toluene inhibitor was again added and reflux continuedfor 4 hours. The precipitate laden mixture was then allowed to cool toroom temperature. The tricarboxylate salt was collected by suctionfiltration, then dissolved in deionized water (800 ml) and neutralizedwith dilute aqueous hydrochloric acid (5:1 conc. HCl/H₂ O vol. ratio) toa pH<2. Two additions of approximately 3000 ml each of anhydrous acetonewas added to the acidified solution and the potassium chlorideprecipitate was filtered off. The acetone was then stripped off and theprocess was then repeated. The remaining volatiles were then removedunder reduced pressure to give an isolated yield of 113.1 g (74.4%) ofan off white solid (mp 112.5°-125° C. decomposed). NMR, infrared andacid dissociation constants data were used to characterize thetricarboxylic acid product. In water, aqueous potassium hydroxidetitration identified the Pka's of the three carboxylic acid groups as2.60; 4.59 and 8.06.

EXAMPLE E 1-(3/4-Vinyl benzyl)-1,1,2-ethane tricarboxylic acid

An aqueous potassium hydroxide solution (6126 g, 109.2 mol of potassiumhydroxide in 2490 g of water) was slowly added to 6375 g (11.17 mol) ofthe unpurified vinyl benzyl triester/ethanol solution of Example B,(36.47% NVM) containing a small amount of butylated hydroxy tolueneinhibitor, while keeping the exothermic reaction below reflux. Anadditional small amount of butylated hydroxy toluene was again added.The mixture was then heated to reflux for 4 hours, and cooled to roomtemperature. The precipitated solid tricarboxylate salt was collected byfiltration. Additional ethanol (12000 g) and then propanol (12000 g)were used to precipitate out the remaining salt which was collected byfiltration.

A dispersion of the tricarboxylate salt was made in anhydrous acetone.The salt was neutralized by acidifying the mixture with a concentratedhydrochloric acid (HCl)/water solution (5:1 volume ratio) to a pH of <2.The acetone, aqueous HCl solution was then treated with a 2:1hexane/toluene mixture. Stripping volatiles from the residual solutionyielded 2777 g of an orange solid crude product. NMR and infraredspectral data confirmed the structure as the desired tricarboxylate. Theproduct also contained some neutralized potassium carboxylate salt.

Another potential utility of the ester monomers of this invention istheir use as polymerizable components of free radical addition polymers.A theoretical production of such a polymer is given in Example F.

EXAMPLE F HYDROXY-FUNCTIONAL COPOLYMER

A representative hydroxy-functional polymer incorporating the styrenebased ester of this invention could be prepared, in a representativefashion, as follows:

A reaction vessel equipped with a mechanical stirrer, water cooledcondenser, nitrogen inlet, water trap, thermometer and heating mantelcould be charged with 172.5 parts of n-butyl acetate and heated toapproximately 230° F. and a monomer premix comprising 91.2 parts ofmethyl methacrylate, 58 parts of butyl acrylate, 58 parts of hydroxyethyl methacrylate, 15 parts of the monomer of Example C, 54 partsstyrene and an initiator premixture composed of 11.5 parts of n-butylacetate and 5.7 parts of 2,2'-azobis(2-methylbutyronitrile) could bemetered simultaneously into the polymerization reactor at a constantrate for approximately 4 hours. The reaction temperature could bemaintained for an additional 2 hours after the addition was completedand then allowed to cool to yield the hydroxy-functional acrylic polymerincorporating the styrene based ester of this invention. Such ahydroxy-functional polymer could be utilized in combination with atypical crosslinking agent, such as a polyisocyanate or a melaminecuring agent to provide curable coating compositions.

While this invention has been described by a specific number ofembodiments, other variations and modifications may be made withoutdeparting from the spirit and scope of the invention as set forth in theappended claims.

The invention claimed is:
 1. A polymer which comprises the free radicalpolymerization reaction product of:(i) 1% to 100% by weight of anunsaturated ester monomer having the structure: ##STR6## wherein R¹ ishydrogen or methyl; R², R³ and R⁴ are each independently lower alkyl ofto about 4 carbons; and Z is nothing or is a divalent radical having 1to about 20 carbons; and (ii) 0% to 99% by weight of at least one otherunsaturated monomer copolymerizable with the unsaturatedester-functional monomer.
 2. The polymer of claim 1 wherein R¹ ishydrogen.
 3. The polymer of claim 1 wherein R¹ is methyl.
 4. The polymerof claim 1 wherein R², R³ and R⁴ are each ethyl.
 5. The polymer of claim1 wherein Z is nothing.
 6. The polymer of claim 1 wherein Z is adivalent polymethylene chain --(--CH₂ --)_(n) --wherein n is 1 to
 20. 7.The polymer of claim 1 wherein the polymer comprises the reactingproduct of 5% to 85% by weight of the unsaturated ester monomer and 15%to 95% of at least one other unsaturated monomer copolymerizable withthe unsaturated ester-functional monomer.